Intelligence, Race, and Genetics

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Intelligence, Race, and GeneticsRobert J. Sternberg, Elena L. Grigorenko, and Kenneth K. KiddYale UniversityIn this article, the authors argue that the overwhelmingNor do any tests, except dynamic tests (see Sternberg &portion of the literature on intelligence, race, and geneticsGrigorenko, 2002a) that require learning at the time of theis based on folk taxonomies rather than scienti?c analysis.test, directly measure ability to learn. Rather, traditionalThey suggest that because theorists of intelligence disagreetests focus much more on measuring past learning, whichas to what it is, any consideration of its relationships tocan be the result of differences in many factors, includingother constructs must be tentative at best. They furthermotivation and available opportunities to learn.argue that race is a social construction with no scienti?cSome theories of intelligence extend this de?nition byde?nition. Thus, studies of the relationship between racesuggesting that there is a general factor of intelligence,and other constructs may serve social ends but cannotoften labeled g, that underlies all adaptive behavior (Brand,serve scienti?c ends. No gene has yet been conclusively1996; Jensen, 1998; see essays in Sternberg & Grigorenko,linked to intelligence, so attempts to provide a compelling2002b). In many theories, including the theories mostgenetic link of race to intelligence are not feasible at thiswidely accepted today (e.g., Carroll, 1993; Gustafsson,time. The authors also show that heritability, a behavior-genetic concept, is inadequate in regard to providing such1994; Horn, 1994), other mental abilities are hierarchicallya link.nested under this general factor at successively greaterlevels of speci?city. For example, Carroll has suggestedthat three levels can nicely capture the hierarchy of abili-Aties, whereas Cattell (1971) and Vernon (1971) suggestednumber of scholars claim to have studied rela-tionships among intelligence, race, and geneticstwo levels that were especially important. In the case of(e.g., Herrnstein & Murray, 1994; Rushton,Cattell, nested under general ability are ?uid abilities of the1995). The thesis of this article is that these studies are notkind needed to solve abstract reasoning problems such asgrounded in scienti?cally derived constructs but rather in?gural matrices or series completions and crystallized abil-folk beliefs about them. There is a big difference betweenities of the kind needed to solve problems of vocabularystudying relationships between constructs and folk beliefsand general information. In the case of Vernon, the tworegarding such relationships. The bigger problem, how-levels corresponded to verbal– educational and practical–ever, is when one studies the latter but believes one ismechanical abilities. What we know about group differ-studying the former.ences largely involves so-called g and major group factors,In this article, we ?rst review the nature of intelli-such as verbal and spatial skills. More modern theoriesgence. We then discuss the relationship between intelli-extend intelligence much further, for example, to creativegence and race. Finally, we re?ect upon the relationshipsand practical as well as analytical abilities (Sternberg,among intelligence, race, and genetics.IntelligenceRobert J. Sternberg, PACE Center, Yale University; Elena L. Grigorenko,PACE Center and Child Study Center, Yale University; Kenneth K. Kidd,To study the interrelationships among intelligence, race,Department of Genetics, Yale University.and genetics, we need to know what intelligence is. We doPreparation of this article was supported by National Science Foun-not know. Hence, any conclusions about its relationships todation Grant REC-9979843; by a government grant under the Javits Actother constructs will be, at best, tentative.Program (Grant R206R000001), as administered by the Institute of Edu-cational Sciences, U.S. Department of Education; by U.S. Department ofFormal Theories of IntelligenceEducation, Institute for Educational Sciences Award 31-1992-701, asadministered by the Temple University Laboratory for Student Success;One way to ?gure out what intelligence is has been to askand by National Institutes of Health Grants AA09379 and GM57672 andexperts. Two major symposia have done so (“IntelligenceNational Science Foundation Grant BCS0096588. Grantees undertakingsuch projects are encouraged to freely express their professional judg-and Its Measurement,” 1921; Sternberg & Detterman,ment. This article, therefore, does not necessarily represent the positions1986). Each of the roughly two dozen de?nitions producedor policies of the U.S. government, and no of?cial endorsement should bein each symposium was different. There were some com-inferred.mon threads, such as the importance of adaptation to theWe are grateful to Julian Elliott, Jeremy Gray, Linda Jarvin, Jenniferenvironment and of the ability to learn, but these constructsJordan, Scott Kaufman, Richard Nisbett, David Preiss, Steven Stemler,and Karin Weis for comments that helped improve this article.themselves are not well speci?ed. Moreover, very few testsCorrespondence concerning this article should be addressed to Rob-of intelligence directly measure either one. Tests do notert J. Sternberg, PACE Center, Yale University, Box 208358, New Haven,offer adaptive tasks one is likely to face in everyday life.CT 06520-8358. E-mail: [email protected]46January 2005 ? American PsychologistCopyright 2005 by the American Psychological Association 0003-066X/05/$12.00Vol. 60, No. 1, 46 –59DOI: 10.1037/0003-066X.60.1.46conventional tests. But it is not clear that tests of IQmeasure the same construct among all people to whom thetests are applied (Sternberg, 2004a, 2004b). The moreculturally distinct the people, the greater the differences inwhat the items measure. In part, this is because IQ testitems are largely measures of achievement at various levelsof competency (Sternberg, 1998, 1999, 2003). Items requir-ing knowledge of the fundamentals of vocabulary, infor-mation, comprehension, and arithmetic problem solving—so-called measures of crystallized abilities (Cattell, 1971;Horn, 1994)—are clearly measures of achievement. Itemsrequiring ?uid abilities (Cattell, 1971; Horn, 1994) involv-ing abstract reasoning, once thought to be culture fair(Cattell & Cattell, 1963), have proven even more suscep-tible to effects of cultural and other environments than testsof crystallized abilities (Flynn, 1984, 1987; Neisser, 1998),suggesting they are in no way “culture fair.” Western-styleschooling even more extensively inculcates these ways ofthinking than it does those measured by tests of crystallizedabilities.Robert J.In summary, it is probably more accurate to refer toSternbergexisting studies as assessing the relation between “IQ” or“psychometric g” and what is labeled as race than asassessing “intelligence” and these other constructs. Doesthe language we use matter? Yes. We need to acknowledge1997; Sternberg et al., 2000) or to eight distinct multiplethat we are using convenient, partial operationalizations ofintelligences (Gardner, 1999a, 1999b).the construct of intelligence, and nothing more. As profes-sionals, some of us may understand that there is a large gapInformal Theories of Intelligencebetween the conceptualization and operationalization ofLay conceptions of intelligence are quite a bit broader thanintelligence. Others of us may act as though IQ testsconceptions of psychologists who believe in g (Berry,somehow provide the kind of measurement of intelligence1974; Sternberg & Kaufman, 1998). For example, in athat a tape measure provides of height. When we arestudy of people’s conceptions of intelligence (Sternberg,dealing with the lay audiences who learn about our work,Conway, Ketron, & Bernstein, 1981; see also Sternberg,it is especially important that we acknowledge that we1985), Sternberg and his colleagues found that laypersonshave nothing even vaguely close to a “tape measure” ofhad a three-factor view of intelligence as comprising ver-intelligence.bal, practical problem-solving, and social competence abil-ities. Only the ?rst of these abilities is measured by con-Intelligence and Raceventional tests. Experts in different occupations in the“Out of Africa”United States have somewhat different conceptions of in-telligence, with their views of the relevant attributes tend-Most scientists who study such matters believe that thoseing to match the requirements of their occupations (Stern-humans of whom we are descendants all lived in Africaberg, 1985). And conceptions of intelligence around the(e.g., Tishkoff et al., 1996; Tishkoff & Kidd, 2004; Walterworld vary even more than they do in the United Stateset al., 2000). They ?rst appeared roughly 200,000 years(Grigorenko et al., 2001; Sternberg, 2004b; Yang & Stern-ago. For whatever reasons—to ?nd food, to satisfy wan-berg, 1997a, 1997b).derlust, to ?nd better protection against predators, to ?ndThe way intelligence is usually de?ned in studies ofmore land—small numbers of unrepresentative peoplethe alleged relationships among intelligence, race, andstarted to migrate out of Africa about 100,000 years agogenetics is in terms of Boring’s (1923) operational de?ni-(Stringer, 1990).tion of intelligence as whatever it is that IQ tests measure.The “out-of-Africa” hypothesis places the ?rst immi-This de?nition is unsatisfactory for at least three differentgrants from Africa in southwestern Asia. Over the coursereasons. First, it is circular, de?ning the construct in termsof tens of thousands of years, that initial non-Africanof the operation and the operation in terms of the con-population expanded until now at least some of its descen-struct. Second, so-called IQ tests do not all measure thedants can be found on all continents and in most regions ofsame thing (Mackintosh, 1998). Third, as indicated, theo-those continents except for Antarctica, which, in general, isrists of intelligence do not themselves agree as to whattoo cold to be hospitable, at least for modern humans. Asintelligence is.people migrated, they adapted so as better to ?t theirFor convenience, we can follow Boring and operation-environments. Much of that adaptation was cultural— dif-ally de?ne intelligence in terms of IQ as measured byferent clothing, different foods, for example— but some ofJanuary 2005 ? American Psychologist47may be very different from those in the parent population.As the new population grows over a few generations, themagnitude of the sampling error per generation decreases,and the new population will continue to have very differentfrequencies from the parent population. This extreme formof random genetic drift is referred to as a “founder effect,”because the population expanded from very few founderswith a relatively restricted gene pool. For example, avail-able evidence suggests that a small group of individuals leftAfrica and over time allele frequencies changed markedlyfrom those in the African populations left behind.The third mechanism is gene ?ow or genetic ex-change, by which interbreeding among certain groups ofindividuals potentially results in those populations becom-ing increasingly similar to each other. Two populations thatstart off quite different genetically, if they mate, can pro-duce offspring that represent the genes present in both ofthe original populations.The fourth mechanism is natural selection, by whichorganisms with gene patterns that are adaptive to a givenElena L.environment become more prevalent over time. For exam-Grigorenkople, organisms that can adapt to changing climatic patternsare at an advantage over those that adapt only with greatdif?culty.Migration and Adaptationit was genetic. However, it is dif?cult to prove that traitsseen to differ are truly the result of different selectiveAlthough all of these mechanisms are of importance, herepressures, that is, genetic adaptations. A major reason forwe illustrate only that of natural selection. Consider thethe dif?culty is that at the genetic level there are quantita-following example. During the Industrial Revolution intive differences in frequencies of genetic variants, notlate-19th-century England, a particular dark-colored mothqualitative genetic differences, among populations. Whenbecame more prevalent than a related light-colored moth.multiple forms of a DNA sequence, either a coding se-Why? It is believed industrial pollution had blackened thequence or a noncoding sequence, are present, the sequenceforests and improved the darker moth’s camou?age againstis referred to as polymorphic and the forms as alleles at thepredators such as birds. The light-colored moth was toopolymorphism. Among populations of various kinds, allelevisible to survive. More recently, however, with restric-frequency differences at polymorphisms are the rule be-tions on air pollution, the light moth has made a comebackcause of the chance effects known as random genetic drift.(Cook, 2003). The point, of course, is that natural selectionIn other words, as a result of both natural and social events,is a constantly shifting process. It is in?uenced not only byonly some genotypes are transmitted through generations;an organism’s biology, but also by the interaction of thatthe others are lost. The lack of predictability in who willbiology with environmental conditions (Sternberg, 2004c).have children and who will not introduces powerful ran-Is it better from the standpoint of adaptation to thedom noise into allele frequencies between generations.physical environment to be a black moth or a light-coloredThus, observing different allele frequencies does not, inmoth? It depends on the interaction between the organism’sand of itself, imply that local selection has operated.attributes, including color, and the particular environment.Is it better from the same adaptive standpoint to be a BlackMechanisms of Genetic Influenceperson or a light-colored person? The answer is the same,Four mechanisms have in?uenced the genetic evolution ofof course. In zones with more intense exposure to sunlight,populations (Templeton, 2002). We consider each in turn.darker skin puts individuals at an adaptive advantage. TheThe ?rst is mutation, by which genes change inmelanin that acts as a pigmentation to produce darker skinrandom ways. Mutation results in the rise of both func-better protects individuals against the damage that largetional (i.e., coding) and nonfunctional (i.e., noncoding)amounts of ultraviolet radiation can cause to the skin. Leftpolymorphisms.unchecked, this radiation increases susceptibility to skinThe second is random genetic drift, by which allelescancer, especially melanoma, a form of skin cancer thatin ?nite populations may change in frequency over time aseasily can become fatal. In zones with weaker exposure toa result of the accumulation of random sampling error insunlight, lighter skin is an advantage.the passing on of alleles from generation to generation.One explanation of lighter coloration pertains to vita-When a very small number of individuals migrate and startmin absorption. People rely on sunlight to produce activea new population, the sampling error (random genetic drift)vitamin D in the capillaries. The active form does not3is very large, and allele frequencies in the new populationoccur in great quantities in the food most people eat.48January 2005 ? American Psychologisthumans indirectly resulted from the pattern of expansionand migrations accompanied by random genetic drift. Overthe years, frequencies of DNA variants changed onlyslightly in terms of total DNA composition but changedenough to produce differences, many of which we still donot fully understand. The changes are numerous. Less than1% of human DNA varies globally, in the 3 billion nucle-otide positions in the human genome; however, that 1%creates a large number of potential differences between anytwo people. Some regional differences are observable, andothers less so. For example, one will see larger proportionsof blond hair and blue eyes in people born in Europeancountries than in those born in Asian ones. In addition, onewill see shorter people, on average, among those born inAsia than among those born in Europe, and one will seewider noses in West Africa, on average, than in EastAfrica. In other words, within geographic groups, there isvariation, and, as it turns out, tremendous variation.Race as a Social ConstructionKenneth K.Where does race ?t into the genetic pattern? Actually, it ?tsKiddnowhere. Race is a socially constructed concept, not abiological one. It derives from people’s desire to classify.People seem to be natural classi?ers. Perhaps this tendencyre?ects, in part, what Gardner (1999a, 1999b) has referredIndeed, often milk is supplemented with vitamin D toto as “naturalistic intelligence.” Or perhaps it merely re-3prevent de?ciencies. Lighter skin allows greater bodily?ects a need to discern order in or even to impose it onproduction of vitamin D . De?ciencies in vitamin D cannature. Any set of observations can be categorized in33cause rickets in children and osteoporosis in adults (O’Neil,multiple ways. People impose categorization and classi?-2004).cation schemes that make sense to them and that, in someA second explanation is of a different kind. There is ascases, favor their particular goals.yet no conclusive evidence of positive selection for lightIf one looks at geographic patterns, one will ?nd manycoloration. Instead, evidence to date may indicate that lightattributes that correlate with geography; nearby populationspigmentation in climates distant from the equator repre-tend to be similar and distant populations dissimilar. Thissents a lessening of the selective factors that lead to darkpattern is similar to common ideas of socially de?ned racespigmentation near the equator rather than to any particularbut is more complex (K. K. Kidd, Pakstis, Speed, & Kidd,factors leading to lighter pigmentation per se (Harding et2004; Rosenberg et al., 2002; Tishkoff & Kidd, 2004).al., 2000). Individual moths or other animals do not radi-People in different places come to demonstrate differentcally change in color in the course of their lifetimes.characteristics by adaptations to different environments,Rather, over time, those descendants that are better adaptedsuch as heterozygosity for sickle-cell hemoglobin as aare more likely to survive and reproduce, and thus distri-partial protection against malaria, as well as by accumula-butions of traits change. Human populations adapt overtion of random genetic drift. But as is so often the case, themany generations, but not all organisms do. Some adaptsame trait that may be adaptive in one circumstance may bevery rapidly. Generations of bacteria, for example, adaptmaladaptive in another. For example, there is no advantagerapidly because of their extremely rapid rates of reproduc-of sickle-cell hemoglobin in the absence of malaria, and thetion. It is for this reason that the same medication, amoxi-anemia that results in homozygotic individuals poses acillin, that was effective in treating ear infections in theserious disadvantage.children of 20 years ago is so much less effective in treatingOther adaptations are equally ?ckle. Today, our pop-ear infections in the children of today. Bacteria haveulation is paying the price of tens of thousands of years inadapted, in the same way that malaria parasites havewhich people became genetically programmed to enjoy fatsadapted to many quinine-based treatments and in the sameand sugars and to eat as much of them as they could whenway that the HIV virus is adapting to the medications beingthey had the opportunity. In the contemporary environ-used to treat it. All biological populations adapt, whetherment, the result is high levels of overweight and obesity.bacterial, human, or anything else.Some people have more of a genetic predisposition to gainThere is another key fact in this story. Aside from theweight than others. Social strati?cation— classifying peo-explanations of skin color, there are not many scienti?callyple into categories of higher and lower status in a society—supportable selective explanations for the differences ob-has already ensued on the basis of weight (Brownell &served in people from different parts of the world. It isHorgen, 2003). Whether, ultimately, people with a geneticprobable that much of the variation seen among groups ofpredisposition toward fatness will be classi?ed as being ofJanuary 2005 ? American Psychologist49a separate race remains to be seen. The point is that anJews who do not view themselves as priests exhibit thisadaptation that is positive at one time or place may bepattern. What conclusion is to be drawn? Well, the correctindifferent at another and negative at still another.conclusion is that different groups of people will differ inOne could pick any of a number of traits correlatedvarious respects. The authors of the study concluded thatwith geographic patterns and ?nd correlations with otherone could infer a genetic Jewish priestly line dating back torelated traits. It would be foolhardy, however, to view anythe biblical Aaron (Skorecki et al., 1997). Other bases forone of these traits as causative of the others. That is whatdifferentiation could be chosen as well, including the afore-people have done who have viewed differences in so-calledmentioned one of girth.races as somehow causative of differences in IQ. It alsoAs another example, Fish (2002) has pointed out thatwould be foolhardy to group fairly arbitrary sets of traitspeople who have lived over many generations in coldand constructs that one then rei?es as being natural, some-climates, such as Eskimos, have tended to develop roundedhow God-given categories. One will ?nd a distribution ofbodies to maintain heat and thus stay warmer. Some pop-traits in any of these groups, with only slightly moreulations in very hot climates, such as the Masai, havedifferentiation in comparisons involving individuals fromtended instead to develop lanky bodies. The hypothesis isdifferent groups than in comparisons involving individualsthat the high ratio of surface area to volume results in theirfrom the same group (K. K. Kidd et al., 2004). Why wouldradiating a high amount of heat and thus staying cooler.people do this, then? One reason is to justify existing socialAlthough reasonable, both adaptation hypotheses lack rig-strati?cations or to create new ones.orous scienti?c proof. Possibly, they could be just coinci-We could of course refer to moths as being of differentdences. Scientists do not know for sure.“races” (black and white) in the same way we sometimesIn the American folk taxonomy of race, as argued byrefer to humans as being of different “races.” We do notFish (2002), lanky and rounded people can represent, re-typically use the term for moths, presumably because wespectively, two kinds of Blacks and Whites. But one couldare less interested in creating social strati?cations for mothsas easily decide that a more “basic” taxonomy of racesthan for people, and race is one way to help create thesewould be in terms of lanky and rounded bodies, in whichstrati?cations. Of course, we recognize that our article maycase there would be Black and White members of the lankyhave the opposite effect from that intended: Some believersand rounded races. One would ?nd a number of geneticin biological race may realize that moths (and perhapspatterns that, on average, correspond to lankiness anddogs, cats, and other animals that come in multiple colors)roundedness, in the same way one would ?nd genetichave been sorely neglected in the literature on racial dif-correlate patterns corresponding to darker versus lighterferences and that there is still time to remedy this situation.skin, Cohens versus non-Cohens, or basketball playersTo the extent we de?ne race as simply different sets ofversus wrestlers.physical features, we could say, of course, that the mothsIt has been argued that the challenges faced by thoseare of different races. But the term, used in this way,who migrated to northern climates were greater than thosebecomes simply a word for saying the moths look different!faced by people in southern climates and that this differ-And the surplus meaning associated with the word, at leastas it is used in human descriptions, vanishes.ence might have led to higher intelligence levels amongOver time, peoples who migrated changed both bythose who went northward (see Rushton, 1995). However,chance and by adaptation to their environments in variousanyone who has spent any signi?cant time in Africa mightways. What is “good” depends on the adaptations that needwell dispute this claim. One of the greatest challenges ofto be made, and these adaptations change from time to timetropical climates is ?ghting tropical diseases to survive, andand place to place. For example, our ancestors in Africathe challenges of ?ghting diseases are greater in the tropicswere almost certainly dark-skinned because dark skin pro-than they are further north. Indeed, children acquire fromvided better protection against the particular challenges ofan early age specialized knowledge, not acquired furtherthe environment, most notably ultraviolet and other harm-north, regarding natural herbal medicines that can be usedful forms of radiation. Other traits, such as straight or curlyto combat tropical illnesses (Sternberg et al., 2001). To thehair, have no evident adaptive value, and population dif-extent that warmer climates encourage greater aggressionferences probably re?ect chance differences. Curiously,(see, e.g., Nisbett & Cohen, 1996), learning how to com-then, socially constructed judgments as to how socially topete successfully so as to survive in such environments alsostratify people are made on bases that have no relation tomight promote intellectual development. We are not argu-the original reasons people came to look one way oring that people in warmer climates did indeed developanother.higher intelligence but, rather, that one could create spec-There is nothing special about skin color that serves asulative arguments supporting greater intellectual growth ina basis for differentiating humans into so-called races. Anysuch climates, as has been done to support the notion thattwo groups of people that differ in one way are likely tothere was greater intellectual growth as a result of chal-differ in a cluster of ways. For example, as noted by Markslenges up north. Indeed, post hoc evolutionary arguments(2002), geneticists have found that 54% of people whomade in the absence of fossils at times can have thehave designated themselves as Hebrew priests, many ofcharacter of ad hoc “just so” stories designed to support, inwhom have the surname of Cohen, have a certain pattern ofretrospect, whatever point the author wishes to make abouttwo genes on the Y chromosome. In contrast, only 33% ofpresent-day people.50January 2005 ? American PsychologistDifferences in socially constructed races stem largelymakes one Black to some degree. So one can be lightfrom geographic dispersions that began about 100,000Black, medium-skinned, or dark Black, but one is stillyears ago and continued until about 3,000 years ago inBlack. Even if individuals of mixed parentage inheritedsome areas. Today we see the physical correlates left bynone of the physical features of blackness, they would stillthese dispersions. Much of that variation is continuousbe classi?ed as Black, although they might pass for Whiteacross distances, but with different traits showing different(Fish, 2002). In areas where Blacks are of higher socialrates and patterns of change. What “race” does is to reifystatus, degrees of whiteness may all be seen as departuresthese differences as deriving from some imagined naturalfrom true blackness.grouping of people that does not in fact exist, except in ourThe concept of race serves a social rather than aheads.biological purpose. Different types of parentage have, atWhat we see in terms of skin color correlates veryvarious times and places, given rise to racial labeling (e.g.,well with our developed folk taxonomies but only weakly“Aryan race,” “German race,” and “Jewish race”). In apart-with genetic differentiations. For example, the amount ofheid South Africa, the races were Bantu (Black African),genetic variation in Africa is enormous and is much greatercolored (including people of perceived mixed descent),than that in the rest of the world (e.g., Tishkoff & Kidd,Indian/Asian, and White. In contemporary North American2004; Tishkoff & Williams, 2002). In contrast, in terms ofsociety, we mix together the Black and colored “races,”the amount of phenotypic variation, or differences in ap-somehow believing, as noted, that individuals who possesspearance, Africa is at least comparable to the rest of theany degree of nonwhiteness should be grouped in the Blackworld. The phenotypic differences are nevertheless notable.category. Hitler designated as a member of the Jewish raceFor example, in Africa, one can ?nd very tall Masai andanyone who had supposed Jewish blood, which could datevery short Pygmies who probably gained an adaptive ad-back to one’s great-grandparents.vantage by virtue of their shortness for locomotion throughIn parts of Brazil, the supposed races are differentforest vegetation (Fish, 2002). Yet, some may lump to-again (Fish, 2002). A loura has straight blond hair, blue orgether all of these Africans as the same, despite the fact thatgreen eyes, light skin color, and a narrow nose and thingenetically they differ more from each other, in manylips. A branca has light skin color, eyes and hair of anycases, than they do from those who perceive themselves tocolor, a nose that is not broad, and nonthick lips. In Brazil,be of higher social, or even biological, value.Fish pointed out, a branca is White. In the United States, aHumans have devised various metaphors for under-branca individual from Brazil would more likely be clas-standing why some people are more successful, accordingsi?ed as “Hispanic.” Then there is a morena, who hasto whatever standards society invents, than others. Usually,brown or black hair that is wavy or curly but not tightlycomparisons are drawn by those who consider themselvescurly and has tan skin, a nose that is not narrow, and lipssuccessful for the bene?t of others who consider them-that are not thin. Morenas in the United States are classi?edselves successful or on the road to success (e.g., seeas Black or Hispanic. There are a number of other BrazilianHerrnstein & Murray’s, 1994, discussion of meritocracy).terms used to describe socially constructed racial catego-A curiosity of history is that people come to believe in theries, such as mulata and preta, and to the Brazilians thesereality of their own metaphors. For example, some haveterms are every bit as real as the Black, White, and Asianbelieved, and some still believe, in “royal blood.” Educatedcategories are in the United States. They are real. But as inpeople probably realize that the expression is metaphorical;the United States, they are folk, not biological, taxonomiesothers probably believe that the blood of royals differs inused to socially stratify people, often in the name of sci-some key respect from the blood of others.ence. At best, the effects are innocuous. At worst, theyFor readers of this journal, a biological concept ofbecome the bases of genocide.“royal blood” probably seems silly. At the same time,People generally use skin color to distinguish races,however, we know that there are distinguishing bloodbut not always. During the genocide in Rwanda, the Hutusgroups. For example, most of us are familiar with the ABOused other physical attributes, such as height, to distinguishand Rh blood-typing systems. According to LewontinTutsis. Because there had been so much intermarriage(1997), there are roughly 35 blood group systems, with 15between Hutus and Tutsis, the distinctions were generallyserving at least somewhat effectively to distinguish differ-weak, and many people were killed simply because theyent human populations. Royal blood, at least within fami-seemed closer to the imagined Tutsi prototype than thelies, may well be distinguishable in terms of blood groups,Hutu one, regardless of their origins. At the time this articlejust as the blood of nonroyal families would. So in thiswas being written, massacres were going on in parts oftrivial sense royal blood can be said to exist, but differentlyDarfur, Sudan, motivated by similar socially constructedin different royal families. In this same trivial sense, theredistinctions.can be differences in distributions of blood groups acrossThe history of the concept of race is inextricablyreligious groups, people with different body shapes, orintertwined with attempts by the winners to explain orpeople with different skin colors.justify why they perceive themselves to be winners. Con-How mixtures are labeled is a function of social status.sider, for example, the term Caucasian. It is an odd term,In the United States, Blacks generally have lower socialin some ways, because although it is used to refer tostatus than Whites, so supposed admixtures of blood de-“Whites,” in Russia people from the Caucuses are consid-termine degrees of “blackness.” Possessing any blacknessered dark relative to many other Russians. Especially be-January 2005 ? American Psychologist51cause of dif?culties in Chechnya and surrounding areas,that race is a socially constructed, not an evolutionarythese dark Caucasians today are viewed with suspicion anddetermined or biologically supported, concept (Smedley,distrust in much of Russia. So the term that is accepted as1993). Of course, science does not ?nd truth by majority“scienti?cally” identifying White people in the Unitedrule. The problem with the concept of race is not that it isStates, often in preference to the term White to give moresupported by only a minority of anthropologists, but that itof a feeling of scienti?c classi?cation, is used in a way thathas no scienti?c basis. Moreover, attempts to link intelli-is largely opposite in contemporary Russia. Where did thegence, race, and genetics have also lacked an adequateterm come from then? It was coined by Johann Friedrichscienti?c foundation.Blumenbach (as cited in Gould, 1994), who chose the nameIntelligence, Race, and Geneticsbecause he believed that the Georgians, from the MountCaucasus region, are the most beautiful race of men (hisThe explosion of genetic research within the past 10 –15words). The term stuck. So people in English-speakingyears has brought the concept of race back to the surface,countries with white skin have the honor of having a namewith some researchers arguing that new molecular datathey imagine to be the formal label for their race, repre-have given the concept of race new signi?cance in thesenting what one naturalist in 1795 believed was the mostcontext of medicine and public health (Risch, Burchard,attractive “race” and what today largely is believed to haveZiv, & Tang, 2002). One might think that, because therather dark as opposed to white skin, according to Russianconcept of race originated as a social proxy for the descrip-standards. Thus, the term is scienti?cally unsupportabletion of biological differences, at least the biologists study-and part of an old racist typology. The term is just as racisting race would agree on its de?nition. However, the realityas Negroid and Mongoloid, terms the politically sensitiveis different. When variation in genetic markers or allelicAmerican will not use.variants is considered, opinions range widely. One view isthat socially de?ned racial differentiation is most pro-Origins of the Concept of Racenounced and even discontinuous when it is evaluated on theWhence emerged the concept of “race”? The concept ofbasis of continental residence (Risch et al., 2002). A secondrace as a classi?cation scheme representing allegedly nat-view is that there is continuity in genetic variation acrossural “types” distinguishable on the basis of clear visualsocially de?ned races and that various races are not dis-attributes such as skin or eye color, hair texture, and certaintinct; rather, there is a single lineage with a shared evolu-facial and bodily features was initially introduced in thetionary fate (Templeton, 1999). According to this view,17th century (Schiebinger, 1993). However, it took thesethere is no biological value in the concept of race (Anon,ideas almost a century to attract the attention of scienti?c2001; Schwartz, 2001). However, in considering these po-“authorities.” According to Gould (1994), Linneaus (insitions, it is important to understand that, even within these1758) ?rst proposed four races: Americanus, Europaeus,extreme views, researchers agree that although human pop-Asiaticus, and Afer, or African. He also alluded to twoulations might differ dramatically in terms of proportionsother categories that did not prove as useful for socialor frequencies of alternative forms of genes (i.e., allelicpurposes as the other categories: wild boys (feral children)variants), they do not differ in the kinds of genes theydiscovered in the forests and monsters, and hairy men withpossess (Snyder, 1951). In fact, both extreme views maylong tails who emerged from tales of travelers. Blumen-have some merit (Tishkoff & Kidd, 2004).bach (1775/1969), building on the work of Linneaus, ?rstA key argument of this article is that race is every bitproposed a grouping of “races,” namely, Caucasians, Mon-as real as royal blood. It exists in some trivial sense as agolians, Ethiopians, and Malays. This early history was nocorrelate of various biological groupings stemming frommore scienti?c than the later history was to be. That is, racemigration and breeding patterns, and no more. However,started out as a not so subtle way of socially classifyingjust as royal families are usually interconnected and dif?-and, ultimately, stratifying people hierarchically, as bettercult to partition off fully, de?ning the boundaries betweenor worse. For example, Linneaus viewed the White asraces is impossible. As The American Heritage Dictionarysanguine and muscular and the Black as phlegmatic andof the English Language (2000) notes in regard to usage,relaxed.“many cultural anthropologists now consider race to beHistorically, the formation of the concepts of race andmore a social or mental construct than an objective biolog-ethnicity was in?uenced by two main perspectives (Kevles,ical fact” (p. 1441).1995). One perspective was formed in the context of theAlthough attempts have been made to establish geneseugenics movement and was used to refer to presumedfor intelligence (Plomin, 1997; Plomin & Spinath, 2004),biological differences between socially de?ned populationsnone have been conclusively identi?ed. A project aimed at(Huxley, 1951). The other perspective was formed in theidentifying quantitative trait loci (QTL) contributing tocontext of physical anthropology and the social sciencesgenetic variation in intelligence (Plomin & Spinath, 2004)and rejected the idea of the biological signi?cance of racialhas attempted to establish QTLs associated with intelli-classi?cations. It argued that race and ethnicity are primar-gence. To date, however, whatever positive ?ndings haveily cultural and historical products of human history (Boas,emerged have either failed to replicate (Chorney et al.,1942). Today, whereas some still defend the basis for the1998; Hill, Chorney, & Plomin, 2002; Hill et al., 1999;“gene-based evolutionary theory” of race (Rushton, 1995),Plomin et al., 1995) or produced weak signals that have notthe majority of cultural anthropologists are in agreementyet been attempted to be replicated with independent sam-52January 2005 ? American Psychologistples (Plomin et al., 2001). Of course, the future may bringFor example, being born with two eyes is 100% underconclusive identi?cations; we simply do not know yet.genetic control (except in the exceedingly rare case ofAs a result, virtually all attempts to study genes re-severe dismorphologies, with which we do not deal here).lated to intelligence have been indirect, through studies ofRegardless of the environment into which a human being isheritability. But heritability is itself a troubled concept. Areborn, he or she will have two eyes. But it is not meaningfuldifferences in intelligence between so-called races herita-to speak of the heritability of having two eyes, becauseble? This question is dif?cult to answer in part because it isthere are no individual differences. Heritability is not 1; itdif?cult even to say what can be concluded from theis meaningless (because there is a zero in the denominatorheritability statistic commonly used. Consider some factsof the ratio) and cannot be sensibly calculated.about heritability (Sternberg & Grigorenko, 1999).Consider a second complementary example, occupa-tional status. It is associated with a statistically signi?cantWhat Heritability Tells Usheritability coef?cient (Plomin, DeFries, & McClearn,1990), but certainly it is not under direct genetic control.Heritability (also referred to as h2) is the ratio of geneticClearly, there is no gene or set of genes for occupationalvariation to total variation in an attribute within a popula-status. How could it be heritable, then? Heredity can affecttion. Thus, the coef?cient of heritability tells us nothingcertain factors that in turn lead people to occupations ofabout sources of between-population variation. Moreover,higher or lower status. Thus, if factors such as intelligence,the coef?cient of heritability does not tell us the proportionpersonality, and interpersonal attractiveness are underof a trait that is genetic in absolute terms, but rather thesome degree of genetic control, they may lead in turn toproportion of variation in a trait that is attributable todifferences in occupational status. The effects of genes aregenetic variation within a speci?c population.at best indirect (Block, 1995). Other attributes, such asTrait variation in a population is referred to as phe-divorce, may run in families (i.e., show familiality), butnotypic variation, whereas genetic variation in a populationagain they are not under direct genetic control; in fact, theis referred to as genotypic variation. Thus, heritability is areason for such familiality may be that these attributes areratio of variation in the phenotype being considered due toculturally “inherited.”relevant genetic variation to phenotypic variation. Herita-bility has a complementary concept, that of environmen-Variation in Heritability Within a Giventality. Environmentality is a ratio of variation in the phe-Populationnotype being considered due to relevant environmentalHeritability is not a ?xed value for a given attribute. Al-variation to phenotypic variation. Note that both heritabil-though we may read about “the heritability of IQ” (e.g.,ity and environmentality apply to populations, not to indi-Herrnstein & Murray, 1994), there really is no single ?xedviduals. There is no way of estimating heritability for anvalue that represents any true, constant value for the heri-individual, nor is the concept meaningful for individuals.tability of IQ or anything else, as recognized by HerrnsteinConsider a trait that has a heritability statistic of 70%; it isand Murray (1994) and most others in the ?eld (e.g.,nonsense to say that the development of the trait in anBouchard, 1997). Heritability depends on many factors, butindividual is 70% genetic.the most important one is the range of environments. Be-Heritability is typically expressed on a 0 to 1 scale,cause heritability represents a proportion of variation, itswith a value of 0 indicating no heritability whatsoever (i.e.,value will depend on the amount of variation. As Herrn-no genetic variation in the trait) and a value of 1 indicatingstein (1973) pointed out, if there were no variation incomplete heritability (i.e., only genetic variation in theenvironments, heritability would be perfect, because theretrait). Heritability and environmentality add to unity (as-would be no other source of variation. If there is widesuming that the error variance related to measurement ofvariation in environments, however, heritability is likely tothe trait is blended into the environmental component).decrease.Heritability tells us the proportion of individual-differenceWhen one speaks of heritability, one needs to remem-variation in an attribute that appears to be attributable tober that genes always operate within environment contexts.genetic differences (variation) within a population. Thus, ifAll genetic effects occur within a reaction range such that,IQ has a heritability of .50 within a certain population, theninevitably, environment will have differential effects on the50% of the variation in scores on the attribute within thatsame genetic structure. The reaction range is the range ofpopulation is due (in theory) to genetic in?uences. Thisphenotypes (observable effects of genes) that a given ge-statement is completely different from the statement thatnotype (latent structure of genes) for any particular at-50% of the attribute is inherited.tribute can produce, given the interaction of environmentAn important implication of these facts is that herita-with that genotype. For example, genotype sets a reactionbility is not tantamount to genetic in?uence. An attributerange for the possible heights a person can attain, butcould be highly genetically in?uenced and have little or nochildhood nutrition, diseases, and many other factors affectheritability. The reason is that heritability depends on thethe adult height realized. Moreover, if different genotypesexistence of individual differences. If there are no individ-react differently to environmental variation, heritabilityual differences, there is no heritability (because there is awill show differences depending on the mean and variancezero in the denominator of the ratio of genetic to total traitin relevant environments (Lewontin, 1974). Thus, the sta-variation in a given population).tistic is not a ?xed value. There are no pure genetic effectsJanuary 2005 ? American Psychologist53on behavior, as would be shown dramatically if a childexample, they may tell us something about the extent towere raised in a small closet with no stimulation. Geneswhich individual differences in the measured intelligenceexpress themselves through covariation and interactionof people in a particular group are associated with geneticwith the environment, as discussed further later.factors. They say nothing about sources of between-popu-lation differences in levels of measured intelligence.Heritability and ModifiabilityLewontin (1972, 1982) provided an illustration of theBecause the value of the heritability statistic is relevantimpossibility of making between-population claims fromonly to existing circumstances, it does not and cannotwithin-population data. Speci?cally, in a study involvingaddress a trait’s modi?ability. A trait could have zero,the use of a set of protein markers (blood groups, serummoderate, or even total heritability and, in any of theseproteins, and red blood cell enzymes) as indicators ofconditions, be not at all, partially, or fully modi?able. Thegenetic differences between populations, Lewontin esti-heritability statistic deals with correlations, whereas mod-mated that roughly 85% of genetic variance occurs betweeni?ability deals with mean effects. Correlations, however,any two individuals within any socially identi?ed racialare independent of score levels. For example, adding agroup; roughly 9% occurs among different populationsconstant to a set of scores will not affect the correlation ofwithin a socially identi?ed race; and only the remainingthat set with another set of scores.6%–7% occurs between socially identi?ed races. OtherConsider height as an example of the limitation of theresearchers have arrived at the same conclusions usingheritability statistic in addressing modi?ability. Height ismore powerful data sets obtained with more technologi-highly heritable, with a heritability level above .90. Yetcallyadvancedmethodologies(Barbujani,Magagni,height also is highly modi?able, as shown by the fact thatMinch, & Cavalli-Sforza, 1997; K. K. Kidd et al., 2004;average heights have risen dramatically throughout the pastRosenberg et al., 2002; Tishkoff & Kidd, 2004) or throughseveral generations.simulation analyses (Templeton, 1999).As an even more extreme example, consider phenyl-Different populations—racial, ethnic, religious, orketonuria (PKU). PKU is a genetically determined, reces-whatever—may encounter quite different environments, onsive condition that stems from a mutation in a single geneaverage. Whatever the heritability of intelligence or otheron chromosome 12 (with a heritability of 1), and yet itsattributes within a given setting, no conclusions can beeffects are highly modi?able. Feeding an infant with PKUdrawn about heritability as a source of differences acrossa diet free of phenylalanine prevents the mental retardationsettings. The fact that IQs have increased so much over thethat otherwise would become manifest. Note also that ayears (Neisser, 1998) suggests that environments differtype of mental retardation that once incorrectly was thoughtwidely over time. They probably differ substantially asto be purely genetic is not. Rather, the mental retardationwell for members of different groups at a given time.associated with PKU is the result of the interaction with anNisbett (1995, 1998) reviewed published studies in-environment (a “normal” diet) in which the infant ingestsvestigating sources of differences in cognitive abilitiesphenylalanine. Take away the phenylalanine and you re-between White and Black individuals. These studies, in-duce the level of— or, in optimal cases, eliminate—mentalvolving designs unlike the behavior-genetic studies de-retardation. Note that the genetic endowment does notscribed earlier, have directly sought to investigate geneticchange: The infant still has a mutant gene causing PKU.and environmental effects on intelligence. For example,What changes is the manifestation of its associated symp-one design has been to look at Black children adopted bytoms in the environment. Similarly, we cannot change (atWhite parents. Of seven published studies, six supportedleast on the basis of our knowledge today) the geneticprimarily environmental interpretations of group differ-structure underlying manifestations of intelligence (or anyences, and only one study did not; the results of the non-other trait); however, we can change those manifestationssupporting study (Scarr & Weinberg, 1976, 1983) wereor expressions of genes in the environment. Thus, knowingequivocal. What the Scarr and Weinberg study did show isthe heritability of a trait does not tell us anything about itsthat IQs of adopted children are more similar to those ofmodi?ability.their biological mothers than to those of their adoptedmothers. Less clear are the “racial” implications of theirWithin-Population Effects Versus Between-?ndings.Populations EffectsMoreover, there is much published evidence indicat-One of the worst intellectual slips made by investigators ofing that heritability estimates vary across populations. Forheredity and environment (or rather, most often, by inter-example, estimates of the heritability of IQ in Russian twinpreters of ?ndings on heredity and environment) is tostudies conducted in the Soviet era tended to be higher thangeneralize the effects of within-population studies betweencomparable estimates in the United States (Egorova, 1988;populations. For example, some investigators have madeGrigorenko, 1990; Iskoldsky, 1988). This observationattributions about effects of racial or ethnic group differ-made sense: Environmental variation in Russia under theences on the basis of behavior-genetic studies (HerrnsteinSoviet regime was constrained; consequently, heritability& Murray, 1994), even while admitting that such conclu-estimates were higher. Most of the IQ heritability studiessions are sometimes ?awed. All of the behavior-geneticup to today have been carried out in various countries of thedesigns used in the studies noted earlier can ascertaindeveloped world. Relatively little information exists re-effects of genetic variation only within populations. Forgarding the heritability of IQ in the developing world,54January 2005 ? American Psychologistalthough some studies suggest that such heritability may bewith a separate expansion into Melanesia and Australia.substantial, at least outside the Western countries that mostAssociated with all of these expansions is accumulatingoften have been studied (Bratko, 1996; Lynn & Hattori,random genetic drift at all polymorphic sites of the ge-1990; Nathwar & Puri, 1995; Pal, Shyam, & Singh, 1997).nome. Thus, allele frequencies generally show gradualRecently, Turkheimer, Haley, Waldron, D’Onofrio, andchanges as one moves around the world. Of course, recentGottesman (2003) showed that heritabilities differ radicallymigrations (over the past few thousand years) of estab-across socioeconomic groups. Obviously, without evenlished populations into already-occupied regions can resultknowing much about estimates of the heritability of IQ inin some adjacent populations having very different alleledifferent populations, we cannot speculate at this pointfrequencies, but that has been rare until historic times.about differences across these populations.Today in the United States, for example, we have popula-In summary, heritability estimates do not explain thetions from very different parts of that geographically con-genetic regulation of behavior and do not provide accuratetinuous spectrum of allele frequencies. These distinct alleleestimates of the strength of this regulation. Heritabilitiesfrequencies do not mean that different “races” exist, onlyare like snapshots of a dancer. They will not tell us eitherthat different parts of a continuum have been sampled. Anwhat the dance is about or what is coming next in theanalogy is the distinction among the colors blue, yellow,dance. The true genetic nature of humans is far from beingand red as samples from a continuous spectrum of light.de?ned. But what is absolutely clear is that genes do not actThese colors have meaning only because the spectral sen-in a vacuum; they act in the environment, and their actionssitivities of the photoreceptors in our eyes and the neuro-can be altered by the environment.logical circuits interpreting the signals interact with a labelarbitrarily imposed on some narrow range of wavelengthsBiological and Genetic Data as Related to thefrom a continuous spectrum.Concept of RaceThere is no question that populations, de?ned geo-One would hope that, because the concept of race wasgraphically, demonstrate dramatic variability in frequen-originally, if falsely, conceived as a concept to signify thecies not only for the several million normal polymorphismsdegree of biological differences between groups of people,not associated with causing genetic disorders but also forthe strongest support for the concept would originate frommany disease-related genetic alleles (variants). The geneticbiological and genetic data. Does it? Here we review somealleles (variants) can be readily seen in ALFRED, theexamples of the relevant research.ALlele FREquency Database (http://alfred.med.yale.med).First, it appears that the global distribution of geneticThe issue is not whether this variation is present or not; thevariation in humans is not easily sorted according to so-issue is whether explaining this variation should occur atcalled races. As reviewed recently (Bamshad et al., 2003;the levels of populations per se (e.g., Lapps, Chuvash,Bamshad, Wooding, Salisbury, & Stephens, 2004; K. K.Nyanja, or Corsicans), continents (e.g., Europe or Africa),Kidd et al., 2004; Tishkoff & Kidd, 2004), scientists haveor alleged races. According to our review of the literature,studied diverse populations for many polymorphisms.variation that seems to be meaningful and transferable intoThese studies involve polymorphisms in the nuclear DNA,helpful public health or educational policies is at the levelincluding variation in the nonrecombining Y chromosomeof speci?c populations. Global socially constructed catego-(Underhill et al., 2000) and autosomal (i.e., located onries such as race do not appear to be useful proxies forchromosomes other than Y and X) markers (e.g., K. K.genetic features.Kidd et al., 2004) as well as polymorphisms in the mito-Second, in considering evidence of a biological basischondrial DNA (Quintana-Murci et al., 1999). A clearfor racial classi?cation, it is important to appreciate com-picture has emerged of the distribution of genetic variationparatively the amount of genetic variation observed withinaround the world, at least in broad strokes. These dataand among speci?c racial categories. In this context, let usoverwhelmingly support the following model for recentturn for an illustration to the research on genetic bases ofhuman evolution and diversi?cation of populations.complex diseases. On the basis of rapidly accumulatingModern Homo sapiens evolved in Africa aboutevidence, a number of geneticists have argued that most200,000 years ago and then spread throughout the rest ofcommon complex diseases, such as diabetes, hypertension,the world and simultaneously diversi?ed starting approxi-cancer, and so forth, appear to be at least partially governedmately 50,000 to 100,000 years ago. During that spreadingby genetic mechanisms shared by most, if not all, popula-out, modern humans supplanted now-archaic humanliketions around the world (Chakravarti, 1999; Daly, Rioux,populations identi?able as having spread outside of Africa,Schaffner, Hudson, & Lander, 2001). This statement hassuch as Neanderthals.triggered a number of large-scale studies, includingThe evidence is that effectively only one populationprojects

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Intelligence, Race, and Genetics

In this article, the authors argue that the overwhelming
portion of the literature on intelligence, race, and genetics
is based on folk taxonomies rather than scientific analysis.
They suggest that because theorists of intelligence disagree
as to what it is, any consideration of its relationships to
other constructs must be tentative at best. They further
argue that race is a social construction with no scientific
definition. Thus, studies of the relationship between race
and other constructs may serve social ends but cannot
serve scientific ends. No gene has yet been conclusively
linked to intelligence, so attempts to provide a compelling
genetic link of race to intelligence are not feasible at this
time. The authors also show that heritability, a behaviorgenetic
concept, is inadequate in regard to providing such
a link.

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